The present invention is with respect to a process and apparatus for making tufts of bristles or single bristles of synthetic resin for brushes, brooms, paintbrushes and the like by producing endless monofilament elements and then winding them directly on a bobbin or guiding them together in groups so that each group has a number of elements equal to the number of bristles in each tuft in the head of the brushes to be produced or part thereof, twisting the group of bristles so produced and winding it on a bobbin, from which the monofilament elements are let off smoothly or in steps and cut to the bristle length and before this or after this each single bristle or each bristle tuft is fixed in position on a brush head.
It is a long time since any important technical developments have been made in the brush, broom and paintbrush making industry. In quite the same way as in the processing of natural bristles, man-made bristles have firstly to be made up into tufts (that is to say if they are not to be fixed in position separately), each such tuft having desired number of bristles therein. These bristle tufts are then fixed in the body or head of the sweeping brush, broom or paintbrush, for example by wedging in place, by using adhesive, by welding (in the case of man-made bristles), by cementing or the like, man-made bristles offering the useful effect from the point of view of production engineering that they may be made as endless monofilament elements by extrusion or melt spinning. The monofilament elements are then guided together as tuft tow, which is packed in paper or metal foil and cut down to the desired length of bristle.
Before such tuft material is able to be used by a maker of sweeping brushes or paintbrushes it has to be unpacked and be placed one piece at a time into the magazine of the machine for making such brushes. While it is in fact true that by using man-made bristle materials brushes may be made more cheaply and simply than when they are made with natural bristles, the manufacturing operation is nevertheless complex. In point of fact--dependent on the sort of process used--about 15 to 30% of the working time of a machine minder is taken up with keeping a machine supplied with bristles.
For some time now attempts have been made at using endless bristle material directly for supplying a brush making machine and doing without the complex steps noted. In such attempts the bristle producer makes an endless tuft of endless monofilament elements that are twisted and wound up on a flanged bobbin so as to be parallel, the twisting operation stopping any later forming of hanging, loose loops. The flanged bobbin is then sent to the brush producer whose brush making machines will have a support for the flanged bobbins, the tuft tow being pulled off from the bobbin roughly tangentially and in steps and run to a cutter for cutting the tuft tow down to the desired bristle length. The cut-off lengths of tow then make their way directly to the wedging tools for fixing the tuft material in the head of the brush. A number of different machines have been designed that are able to be run on such endless tuft material without however coming into anything like wide use in the industry.
Processes on these lines or of generally the same sort have the shortcoming that, if the bobbins are made with a reasonable size and a weight such that they may be readily handled without their diameter being greater than a certain limit only a relatively small amount of bristle material may be stored and transported thereon. The outcome of this is that the tuft tow made up of the monofilaments has to be coiled with a generally small radius, that is to say sharply bent, more specially on the inner part of the flanged bobbin. However because of the low creep resistance of synthetic resins in general and more specially of the resins or plastics used for making bristles, if the bobbin is stored for a long stretch of time the material will be permanently bent or curled, and this will not be overcome by the resilience of the bristle material. It is hardly possible for the bristles to be changed back into their straight form again. This being the case, the material is only able to be kept wound on such bobbins for a short time.